The recent years, solid rocket motor exit cones have been going through a material transition. Initially, common structural materials, such as steel, aluminum and fiberglass, were used, with insulation to protect these materials from the high temperatures of the rocket motor exhaust. More recently, carbon-carbon exit cones have been developed. These structures can carry the operating pressures and thermal loads of solid rocket motors while operating at temperatures in the range of 4000.degree. to 5000.degree. F.
The carbon-carbon exit cones present certain problems in manufacturing. In order to attach these cones to the rest of the motor structure, i.e., to the throat portion of the rocket motor, a threaded cylindrical section is required. If the exit cone were wholly conical, fabrication would be simpler, requiring little more than helically wrapping a suitable resin-impregnated woven carbon fiber cloth around a conical mandrel, curing the resin to make the assembly freestanding, and carbonizing the freestanding assembly. Since, however, a cylindrical attaching section is required, the transition from the cylindrical section to the conical section introduces distortion of the carbon cloth. Such distortion may lead to flaws in the cylindrical section which are difficult to identify by nondestructive testing techniques. The resulting product may be an exit cone with a structurally sound conical section, but with a marginally adequate cylindrical section. It is the cylindrical section where the highest loads occur.
Accordingly, it is an object of the present invention to provide an improved exit cone for a solid rocket motor.
Other objects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, the appended claims and the accompanying drawing.